The present invention relates to an electronic circuit assembly which includes a printed circuit base plate and an electronic circuit element.
More particularly, the present invention relates to improvements in an electronic circuit assembly which is coated with coating material (e.g., plastic resin).
A conventional electronic circuit assembly includes an electronic circuit element and a printed circuit base plate. The electronic circuit element includes a body portion and a plurality of lead pins. The body portion is protected by a molded plastic housing. The plurality of lead pins extend from the body portion and connect the electronic circuit element to the printed circuit base plate.
FIGS. 1 through 3 show a conventional dual in line (DIP) package constituting the electronic circuit element. Such an electronic circuit element includes a housing 10 for an IC constituting the body portion and a plurality of "L" shaped lead pins 12 which extend laterally from the IC housing 10 are bent substantially perpendicularly, as shown in FIG. 3. The lead pins 12 are inserted into holes defined within a printed circuit base plate (not shown in drawings). The lead pins 12 are electrically connected and secured to the printed circuit base plate by soldering.
However, such an electronic circuit element is easily damaged by heat. To prevent thermal damage to electronic circuit element, the electronic circuit element should be placed from the surface of the printed circuit base plate.
To provide such spacing, the lead pins 12 include tapered portions 121 thereon, so that each lead pin 12 has a tip portion which is thinner than a base portion, as shown in FIG. 2. When the tip portions of the lead pins 12 are inserted into the holes defined in the printed circuit base plate, the tapered portions 121 prevent the base portions of the lead pins 12 from being inserted into the corresponding holes. As a consequence, the IC housing 10 is spaced at a predetermined distance from the printed circuit base plate by the tapered portions 121 of the lead pins 12.
Further, to make the electronic circuit assembly water proof and dust resistant, the electronic circuit assembly is coated with an acrylic resin, or the like, as disclosed in Laid-Open Japanese Utility Model application No. 59-107166. However, when such an electronic circuit assembly is coated with a plastic resin, the plastic resin enters the space defined between the IC housing 10 and the printed circuit base plate. When the plastic resin hardens within the space, it shrinks and pulls the IC housing 10 toward the printed circuit base plate. As a result, the lead pins 12 are subjected to a mechanical strain, which degrades the connecting condition between the lead pins 12 and the printed circuit base plate.